Latitudinal distributions and temporal changes of stratospheric HCl and HF

Hydrogen chloride and hydrogen fluoride are important sinks in the stratosphere for free halogens. The major sources of chlorine and fluorine in the stratosphere are anthropogenic; therefore a measurement of HCl and HF gives information about the magnitude of anthropogenic effects on stratospheric chemistry and may give some information about the stratospheric hydroxyl concentration as well. We have determined the total column amount of HCl and HF above 12 km by measuring infrared absorption spectra with a high‐resolution Fourier transform spectrometer flown on a jet aircraft. The HCl column varies from 0.7×10 15 molecules‐cm 2 near the equator to 2.7×10 15 molecules‐cm 2 at 70°N; the HF column is about a factor of 5 lower. The HCl: HF ratio is almost independent of latitude, and neither constituent shows substantial seasonal or diurnal variation. At mid‐latitudes the data from 1978 to 1982 show an annual increase of 5% per year for HCl and 12% per year for HF.